Low smoke density fire-retardant resins

ABSTRACT

Curable aliphatic polyester resin compositions formed from aliphatic unsaturated polycarboxylic acids and polyols and a crosslinking aliphatic vinyl monomer are disclosed. The degree of unsaturation in the polyesters is carefully controlled so that the resin can be cured to produce strong thermoset products. Resins of this nature can be filled with high levels of aluminum hydrate to give compositions that have high oxygen indices and very low smoke densities as measured by the National Bureau of Standards Smoke Chamber. Also, the resins are capable of room temperature curing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is in the field of unsaturated polyesters curable with anunsaturated monomer, and more particularly, is in the field of low smokedensity polyesters.

2. Brief Description of the Prior Art

Traditionally, fire-retardant polyesters have been made with chlorinatedor brominated materials, or, in some cases, phosphorus-containingmaterials. These materials may be merely additives to the polyester orthey may be actual reactants. Although polyesters prepared with suchmaterials are fire-retardant in the sense that they have low flamespreads and are self-extinguishing, they unfortunately emit a thick,dense smoke when exposed to an open flame. The high smoke levels are, ofcourse, undesirable and often are more serious than the fire itself.

We have found that high smoke levels are due not only to the presence ofhalogen-containing or phosphorus-containing materials in the polyester,but are also due to aromatic components in the cured polyester.Aromaticity may be introduced into the cured polyester from thecrosslinking monomer or from the ingredients used to prepare thepolyester itself. An example of an aromatic crosslinking monomer isstyrene which is by far the most widely used crosslinking monomer.Examples of commonly used aromatic ingredients used to prepare thepolyester are the various isomers of phthalic acid, and Bisphenol A.

We have found that completely aliphatic polyester resins made fromunsaturated aliphatic polyesters cured with aliphatic vinyl crosslinkingmonomers such as methyl methacrylate produce very little smoke whencured thermosets are exposed to an open flame. Unfortunately, many ofthese all-aliphatic polyester thermosets are weak, having low flexuralstrength and flexural modulus.

The weakness of polyesters cured with aliphatic monomers such as methylmethacrylate is well known in the art. It is believed that theunsaturated polyesters and methyl methacrylate do not copolymerizereadily and, therefore, give a composition in which some of thepolyester remains unreacted in a mixture of polymethyl methacrylate andsome loosely formed polyester-methyl methacrylate copolymer. See, forexample, "Factors Affecting Durability of Glass-Reinforced PolyesterResins" by A. C. Smith and J. R. Lowry, Plastics Technology, June 1959,pages 42-56. This lack of strength and related properties due to poorcopolymerization or curing has been a principal reason why methylmethacrylate has not been more widely used for the curing of unsaturatedpolyesters.

SUMMARY OF THE INVENTION

We have found that unsaturated polyesters can be fully cured orcopolymerized with aliphatic crosslinking monomers such as methylmethacrylate to produce strong thermoset articles. The key to achievingcomplete curing is to use an unsaturated polyester having a high degreeof ethylenic unsaturation. When these highly unsaturated polyesters arecured with an aliphatic vinyl crosslinking monomer such as methylmethacrylate, strong thermoset articles result. The cured resins producelittle smoke when burned and when filled with aluminum hydrate have lowflame spreads and have surprisingly high oxygen indices.

The resins of the present invention can be cured at elevatedtemperatures, that is, 82° C. and above, and can be made roomtemperature curable.

Besides resinous mixtures, cured thermoset articles are also includedwithin the scope of the present invention. Particularly strong thermosetarticles, useful as articles of construction, can be prepared byreinforcing the cured resinous products of the invention with fiberglass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the effect of hydrated alumina loadings onoxygen index of two polyester resins;

FIG. 2 is a graph showing the effect of the degree of unsaturation inthe polyester on flexural strength;

FIG. 3 is a graph showing the effect of the degree of unsaturation inthe polyester on flexural modulus; and

FIG. 4 is a graph showing the effect of the degree of unsaturation inthe polyester on Barcol Hardness.

DETAILED DESCRIPTION

The present invention relates to a curable aliphatic polyester resin andto cured resinous products prepared therefrom. The resin comprises amixture of an unsaturated aliphatic polyester and an aliphatic vinylmonomer copolymerizable with the polyester. The term "aliphatic" meansthe polyester resin of the present invention is essentially free ofaromatic constituents, although a minor amount, for example, less than 2percent by weight based on resin weight, of aromatic materials may beused as catalyst, accelerators, inhibitors and the like.

The unsaturated aliphatic polyesters are derived from condensing organicpolycarboxylic acids having a functionality of at least 2 with organicpolyols having a functionality of at least 2. The unsaturated componentin the polyester is an alpha, beta-ethylenically unsaturated organicpolycarboxylic acid and the equivalent ratio of alpha,beta-ethylenically unsaturated polycarboxylic acids to all otherpolycarboxylic acid components in the polyester is at least 1 to 1, andpreferably at least about 2.5 to 1, and in certain cases, all theorganic polycarboxylic acid components may be alpha, beta-ethylenicallyunsaturated.

The aliphatic polyesters of the present invention when cured with analiphatic vinyl crosslinking monomer produce strong thermoset articleswhich, when subjected to an open flame, produce little smoke. The amountof smoke generated by burning a cured resinous sample of the inventioncan be determined by measuring the smoke density according to ASTMD-2843. Briefly, the testing procedure involves inserting a specimen ofaccurate, predetermined dimensions inside a smoke chamber. The chamberis substantially air-tight and contains a photocell in the ceiling and astandardized light source in the floor which cooperate with one anotherto measure the optical transmission through the height of the chamber.The specimen is then exposed to an open flame and burned, or, in anotheraspect of the test, the specimen can be subjected to a source of radiantheat and permitted to smolder. In both aspects of the test, the samplesare subjected to combustion and the smoke that is generated is collectedin the chamber. During the course of the test, which usually lasts about20 minutes, the optical transmission is constantly recorded, and theminimum value is taken as a measure of the smoke density. The smokedensity is a logrithmic function of the optical transmission as is shownby the following table:

    ______________________________________                                        Smoke Density (D.sub.m)                                                       Conversion of percent Transmittance to Smoke Density                          Percent Transmittance D.sub.m                                                 ______________________________________                                        75                     16                                                     42                     50                                                     17.5                  100                                                     3.0                   201                                                     0.52                  301                                                     0.090                 401                                                     0.016                 501                                                     0.0028                601                                                     0.00049               701                                                     ______________________________________                                    

Cured aliphatic polyesters of the present invention when burned asdescribed in ASTM D-2843 have smoke densities of about 200 or less,preferably 100 or less. Smoke densities of about 100 are equivalent tooptical transmissions of about 18 percent. At this level oftransmission, one could at least see a lighted exit sign in case of afire. As a point of comparison, highly aromatic systems such as styrenecured polyesters have smoke densities of 300 and above and often 500 andabove. Aromatic, chlorinated and brominated self-extinguishing polyesterresin systems have smoke density values of about 800 and above andfurther, emit toxic vapors of chlorine and bromine or related compounds.The aliphatic polyester resins of the present invention are not likelyto emit effluents of such toxicity.

Besides generating little smoke when burned, the cured aliphaticpolyester resins of the present invention are quite fire retardant asevidenced by their high oxygen indices and their low flame spreads whenfilled with about 50 percent by weight or more hydrated alumina.

The oxygen index is determined according to ASTM D-2863. In generalterms, the oxygen index of a material is percentage by volume of oxygenin the atmosphere necessary to support combustion of the material. Forexample, air contains 21 percent by volume oxygen. If a material burnedin air, it would have an oxygen index of 21 or lower. The higher theoxygen index of the material, the harder it is to get the sample toburn. Thus, the oxygen index is a measure of the fire retardance of thesample. Cured resinous materials of the invention containing hydratedalumina have oxygen indices of at least 35 and preferably at least 50which is easily obtainable when the resin contains from about 50 to 75percent by weight hydrated alumina filler. Hydrated alumina is aparticularly desirable filler because, although it raises the oxygenindex, it does not appreciably affect the smoke density.

Besides oxygen index, flame spread is another indication of fireretardance. The flame spread characteristics of the polyesters of thepresent invention can be determined according to the Underwriters'Tunnel Test (ASTM E-184).

According to the ASTM manual, the Underwriters' Tunnel Test is forevaluating the burning characteristics of building materials and isapplicable to any type of building material. The purpose of the test isto determine the comparative burning characteristics of the materialunder test by evaluating the flame spread over its surface.

The test chamber is a horizontal duct, 171/2 inches wide, 121/2 incheshigh and 25 feet long. Red oak is the calibration standard and isarbitrarily assigned a value of 100. A value of 0 is assigned toasbestos. Other materials are reported proportionately.

It has been suggested that the following classifications be assigned tothe various flame-spread ratings:

    ______________________________________                                        Flame Spread   Classification                                                 ______________________________________                                         0-25          Class A, non-combustible                                       25-75          Class B, fire-retardant                                        75 and up      Class C, combustible                                           ______________________________________                                    

The Underwriters' Tunnel Test is a good measure of flame spread,however, the test is expensive to set up and to conduct.

There is a laboratory scale test which gives an indication of flamespread. The laboratory scale test is referred to as the Monsanto TunnelTest and is described in J. of Paint Technology, 39, (511), 494 (Aug.1967). In the Monsanto Tunnel Test, a sample 2 feet by 33/4 inches isslanted at an angle of about 45° from the horizontal. A specified heatsource is burned at the bottom of the sample and the sample is thenburned for four minutes. The flame spread or how far the flame spreadsup the sample is reported.

It has been found that cured polyester resins of the invention haveflame-spread ratings less than 50 as determined by the Monsanto TunnelTest.

The polyesters of the present invention can be cured to form a strong,hard, thermoset article with an aliphatic vinyl crosslinking monomersuch as methyl methacrylate. As has been mentioned above, this is veryunusual since methyl methacrylate usually only gives partial cures withunsaturated polyesters resulting in weak thermosets of low hardness.Complete cures with aliphatic crosslinking monomers can be insured ifthe polyester contains a high degree of ethylenic unsaturation such asthat specified above. Such resins completely cure with methylmethacrylate to produce strong thermoset articles of high hardness. Theeffect of unsaturation on strength and hardness can be seen in FIGS. 2,3 and 4 which are plots of flexural strength (FIG. 2), flexural modulus(FIG. 3) and Barcol Hardness (FIG. 4) versus percent maleicunsaturation.

The polyester resins evaluated for the data depicted in FIGS. 2, 3 and 4are described in Working Examples 35-41 infra. Briefly, the polyesterswere ethylene, propylene, adipate, maleate polyesters in which themaleic anhydride to adipic acid mole ratio was varied over the range of10-4 to 0-6. Fifty parts by weight of the various polyesters were curedwith 50 parts by weight of methyl methacrylate and 7 parts by weight ofN-vinyl pyrrolidone. FIGS. 2, 3 and 4 show that stronger, harder resinsare obtained with higher levels of unsaturation indicating more completecuring at the higher levels of unsaturation. This trend with aliphaticcuring agents such as methyl methacrylate is opposite to that observedwith aromatic curing agents such as styrene. At high levels ofunsaturation, styrene cured systems become increasingly embrittled andlose strength.

In view of the excellent strength and fire-retardant properties reportedabove, the cured polyester resins of the present invention areparticularly desirable for use as materials of construction, that is,they can be used as molding resins or laminating resins, although, ofcourse, they could be used as coating compositions. However, the resinshave been particularly formulated for use as materials of constructionsuch as automobile and truck body components, liners for truck walls,aircraft parts, boat hulls, plumbing fixtures, piping, duct work and thelike.

The polycarboxylic acids used in the practice of the invention arealiphatic and preferably dibasic and have a high content of alpha,beta-ethylenic unsaturation, that is, the equivalent ratio of alpha,beta-ethylenically unsaturated polycarboxylic acid in the polyester toall other polycarboxylic acids is at least 1 to 1 and preferably atleast 2.5 to 1. Of course, the entire polycarboxylic acid component canbe alpha, beta-ethylenically unsaturated, and the present claims areintended to cover this embodiment.

Examples of alpha, beta-ethylenically unsaturated polycarboxylic acidsare maleic acid, fumaric acid, aconitic acid, mesaconic acid, citraconicacid, itaconic acid and alkyl derivatives of such acids. The anhydridesof these acids where anhydrides exist are embraced within the term"acid" since the reaction products produced therefrom, that is, thepolyesters, are the same. Maleic acid and fumaric acid are preferredacids.

Other polycarboxylic acids and anhydrides can, of course, be used.Examples would be acyclic polycarboxylic acids and anhydrides,preferably dibasic acids and anhydrides. Among the acyclic saturateddicarboxylic acids can be mentioned those which are saturated and whichcontain from about 2 to 10 carbon atoms such as succinic acid, adipicacid, suberic acid, and the like.

Polyesters prepared from symmetrical glycols such as ethylene glycol,neopentyl glycol and the like have a tendency to crystallize and to beonly moderately soluble in crosslinking monomer. The incorporation of anacyclic saturated polycarboxylic acid in the polyester formulationreduces the tendency of the polyester to crystallize, makes the resinmore soluble in crosslinking monomer and lowers the viscosity of theresultant resin.

The tendency of the polyester to crystallize can be minimized byincorporating a branched glycol into the formulation. However, alkylbranching had an adverse effect on oxygen index.

The effect of branching in the polyester chain on oxygen index can beseen in FIG. 1 which is a plot of oxygen index versus percent hydratedalumina content. The two plots in the figure represent differentpolyesters. Plot A represents an ethylene, propylene, maleate, adipatepolyester prepared in the mole ratio of 9/2/8/2. Plot B represents apropylene-fumarate polyester prepared in a molar ratio of 11.5/10. Fiftyparts by weight of the polyesters were combined with 50 parts by weightof methyl methacrylate, filled with hydrated alumina in the variouspercentages shown in FIG. 1 and cured as generally described in Examples28-34 infra. The data in FIG. 1 shows that regardless of the hydratedalumina loading, the polyester resin A with less alkyl branching has ahigher oxygen index than resin B.

The organic polyol component used to prepare the polyester is alsoaiphatic and preferably is difunctional. The polyol can be an alkyleneglycol or an alkylene oxide glycol containing from 2 to 10 carbon atomssuch as ethylene glycol, propylene glycol, butylene glycol, diethyleneglycol, triethylene glycol, dipropylene glycol, neopentyl glycol or thelike. Mixtures of polyols can obviously be used.

Also, in certain preferred embodiments, alcohols and polyols containingallyl or acrylic substitution can be included in the polyol component ofthe polyester. Examples include the monoallyl or diallyl ether oftrimethylol propane, the monoallyl or diallyl ether of glycerol, thediallyl or triallyl ether of pentaerythritol. These components have beenfound to speed the cure of the polyesters cured with aliphatic monomers.In the embodiments where these allyl substituted alcohols and polyolsare used, they should be used in amounts of up to 25 percent by weightbased on total weight of the resin.

A minor amount of the polycarboxylic acid or polyol component, that is,less than about 15 percent by weight, may have a functionality greaterthan 2. This may be in the polyol component and can be glycerine,pentaerythritol, hexanetriol or trimethylol propane. Polyfunctionalmaterial may also be in the acid component and can be, for example,citric acid.

In producing polyesters from the organic polycarboxylic acids andpolyols, the equivalent ratio of polyol components to acid components isgenerally from about 1 to 1.3:1. A slight excess of polyol is normallyused because some is usually volatilized or decomposed during theesterification.

The aliphatic vinyl monomer copolymerizable with the polyester is analiphatic material containing at least one ##STR1## and preferably inthe terminal position. Examples include esters of organic and inorganicacids, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinylisobutyrate, vinyl valerate, vinyl caproate, vinyl enanthate; methylmethacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, amyl methacrylate, hexyl methacrylate, heptylmethacrylate, octyl methacrylate, decyl methacrylate; methyl acrylate,ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate,isobutyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate,heptyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decylacrylate, and dodecyl acrylate; allyl formate, allyl acetate, allylpropionate, allyl butyrate, allyl valerate, allyl caproate,allyl-3,5,5-trimethyl hexoate, allyl acrylate, allyl crotonate, allyllactate, allyl acetoacetate, as well as methallyl esters correspondingto the above allyl esters, as well as esters from such alkenyl alcoholsas beta-ethyl allyl alcohol and beta-propyl allyl alcohols. Also, esterssuch as dimethyl maleate, diethyl maleate, diallyl maleate, dimethylfumarate, diethyl fumarate, dimethallyl fumarate and diethyl glutaconatecan be employed. Also, aliphatic nitriles such as acrylonitrile andmethacrylonitrile can be employed. Obviously, mixtures of monomers canbe used.

A preferred, rapid room temperature curing system employs up to 20percent, and preferably from about 5 to 20 percent N-vinyl pyrrolidonein the vinyl monomer component; the percentage by weight being based ontotal weight of the vinyl crosslinking monomer. By room temperaturecuring is meant the curing is accomplished without the addition ofexternal heat such as would occur at normal room temperatures, that is,from about 20° to 27° C.

With regard to the ratio of polyester to crosslinking monomer, about 40to 70 percent by weight polyester and about 30 to 60 percent by weightaliphatic crosslinking monomer should be employed, the percentages byweight being based on total weight of the polyester and crosslinkingmonomer. The amount of polyester and crosslinking monomer should bevaried with one another in amounts sufficient to provide liquid,flowable, interpolymerizable mixtures which cure to form strongthermoset products. If the amount of polyester is too high or the amountof crosslinking monomer too low, resins of extremely high viscositywhich produce insufficiently cured products will result. On the otherhand, if the amount of crosslinking monomer is too high and the amountof polyester too low, cured products with unsatisfactory properties willresult.

As has been described above, the polyester and crosslinking monomer arethe principal components of the resinous systems of the presentinvention. However, another important component is hydrated aluminafiller. The hydrated alumina increases the oxygen index and decreasesthe flame spread of the cured resinous products of the invention. Theeffect of hydrated alumina on the oxygen index of cured polyester resinscan be seen in FIG. 1 which, as described above, is a plot of percenthydrated alumina versus oxygen index. The graph shows that for twodifferent polyester resins, the oxygen index goes up as the hydratedalumina content of the polyester resin goes up.

The hydrated alumina content of the polyester resin should be about 25to 75 percent, and preferably from about 50 to 70 percent by weight,based on total weight of the polyester resin and the hydrated alumina.Amounts less than 25 percent by weight, although contributing desirableproperties, do not provide the optimum fire-retardant properties desiredin the products of the invention. Higher hydrated alumina contents, thatis, higher than 75 percent, are undesirable because of resulting highresin viscosities.

Besides hydrated alumina, other fillers or pigments may be included inthe resin formulation, although the total filler content should notexceed 80 percent by weight, based on total weight of filler and resinbecause of viscosity considerations. Examples of other fillers includecalcium carbonate, diatomaceous earth and clay. Examples of pigments areTiO₂, transparent iron oxide and phthalocyanine pigments.

Polyester resins of the present invention are cured through additionpolymerization of the unsaturated monomer with the unsaturation sites inthe polyester molecule. This polymerization is free radical initiated.Suitable free radical addition polymerization catalysts include benzoylperoxide, tertiary butyl perbenzoate, tertiary butyl hydroperoxide,cumine hydroperoxide, azo bis(isobutylronitrile), methyl ethyl ketoneperoxide and the like. The catalyst is generally used in amounts of upto 0.1 to 2 percent by weight based on total weight of resin (polyesterplus monomer); the amounts varying with the activity and amount of anyaccelerator and inhibitor used in the resinous system.

Accelerators are used in room temperature curing systems where it isdesirable to initiate the polymerization without the application ofexternal heat. Suitable accelerators include cobalt salts such as cobaltoctoate or cobalt naphthenate. The amount of accelerator used can varywidely, but is usually within the range of 0.1 to 1 percent based ontotal weight of polyester resin.

To prevent any tendency for premature gelation, a gelation inhibitor maybe incorporated into the polyester resin system. Suitable inhibitors areselected from the quinone and phenolic compounds and includepara-benzoquinone, hydroquinone and 4-tert-butyl catechol. The amount ofinhibitor required in the mixture is susceptible to wide variation butpreferably is in the range of 0.001 to about 0.1 percent by weight basedupon weight of the polyester component.

When the polyester resins of the present invention are used as materialsof construction, such as laminating and molding resins, they can bereinforced with glass fibers or other common reinforcements such assteel wire, boron fibers, wood and vegetable fibers. However, because ofstrength and cost considerations, fiber glass reinforcement ispreferred. Fiber glass for reinforcement of polyester resin systems iswell known in the art and a detailed description of the various types ofglass fibers is not considered as a necessary part of the detaileddescription of the present invention. If such a detailed description isdesired, reference is made to Reinforced Plastics, Theory and Procedureby M. W. Gaylord, copyrighted 1969 by Koppers Co., Inc., pages 47-72.

In general, where the resins of the present invention are reinforcedwith glass, about 10 to 70 percent by weight glass fibers based on totalweight of the polyester resin (polyester plus crosslinking monomer plusfiller) should be used.

Besides the ingredients mentioned above, other materials may be added tothe resinous mixture. Examples include mold release agents such as zincstearate or ultraviolet light stabilizers such aso-hydroxyphenylketones, and 2-(2-hydroxyphenyl)benzotriazoles. Theamounts of these other additional components are quite small and do notgenerally in combination exceed about 3 percent by weight of the totalweight of the resinous system.

Polyester resins of the present invention are prepared by techniqueswell known in the art. For example, the organic unsaturatedpolycarboxylic acid can be mixed with the organic polyol materials andthe mixture heated gradually to about 150° to about 230° C. Anesterification reaction catalyst can be employed such as dibutyltinoxide. The reaction mixture is maintained within this temperature rangeuntil esterification is completed, with accompanying evolution of andevaporation of water. A solvent may be used, such as xylene or toluene,to distill azeotropically with the water of the reaction.

The polyesterification reaction can also be conducted withoutazeotroping agents as, for example, by means of a fusion process inwhich a non-reactive gas is blown through a reaction mixture in order toremove the water. Such a process is described in U.S. Pat. Nos.3,109,831, 3,109,832 and 3,109,834.

EXAMPLES 1 - 10

A series of unsaturated polyesters cured with various unsaturatedmonomers, and in some cases, filled with hydrated alumina and reinforcedwith fiber glass were prepared. The catalyst system, time andtemperatures of cure, amount and type of filler, amount of fiber glassreinforcement, as well as certain physical properties of cured resincastings are reported in Table I below.

In all cases, the polyester was an ethylene-propylene-maleateadipate.The method of preparation was as follows:

To a suitable reaction vessel equipped with a condenser, stirrer,thermometer and a source of nitrogen purging (to assist in removal ofwater formed in the condensation) was charged ethylene glycol, propyleneglycol, maleic anhydride and adipic acid in a molar ratio of 9/2/8/2.

The charge was heated to about 100° C. to melt the maleic anhydride,after which time the reaction mixture exothermed, the highesttemperature being 140° C. The reaction was continued at a temperature of210° C. with a moderate nitrogen sparging and heat being applied todrive off water formed in the condensation. Samples were taken offperiodically until the polyester attained a reduced Gardner-HoldtViscosity of G-H, as a 60 percent solution in ethyl CELLOSOLVE. At thisviscosity, the polyester had an acid number of 27-28.

At the completion of the reaction, the polyester at a temperature ofabout 210° C. was kept under a nitrogen atmosphere and cooled to 155°C., at which time inhibitors and modifiers were added. At about 90° C.,the crosslinking agent is added to form the resin solution which is thencooled to room temperature and filtered to remove any gel particles.

    Table I                Heat             Modified   Distor-          934     Smoke Monsanto   tion  % % Methyl % Resin/  Visc-   Barcol Oxy- Den-     Tunnel PSI×10.sup.3 PSI Temp- Ex. Poly- Meth- Comon- Filler  osity     %  Hard- gen sity Test Flexural Flexural erature No. ester acrylate omer R     atio Filler (cps.) Glass Catalyst Cure ness Index D.sub.m F-S Front Back S     trength Modulus (° F.)  1 70 30 -- 1:1 AH 1450       -- BPO 30'/180° F. 57 35.7  97/268      2 50 50 -- 1:1 AH 450     20 .2 VD-1      ##STR2##      52 43.4 72/93 54   48   21.02 13.52 541         .1 DMA oven     (283° C.)         1.0 DDM         0.5 TBP 3 50 25 25 1:1 AH 450     20 BPO 30'/180° F. 55 33.0 159/197    STY 4 60 -- 40 1:1 AH 2450     20 .2 VD-1      ##STR3##      49 31.2 319/424   17.11  8.98 592    STY     1.0 DDM oven     (311° C.) 5 50 50 -- 1:1 AH 350 19 BPO 30'/180° F. 40 43.8     102/203 46.5 30.6 16.59  8.13 532                  (278° C.) 6 45     45 10 1:1 AH 320 20 .5 BPO 30'/180° F. 42 46.5 113/166 41.7 30     19.12 11.79 512    EA     .5 TBP         (267° C.) 7 50 45 5 1:1     AH 450 19 BPO 30'/180° F. 58 42.8 171/232 24.8 36.2 19.79 12.40     570    NPGDA              (299° C.) 8 50 50 -- 1:1 90 AH 980 20     BPO 30'/180° F. 38 43.3  86/185 61   93   22.8   9.6 494      10     Sb.sub.2 O.sub.3            (257° C.) 9 50 50 -- 1:1 90 AH 2500     20 BPO 30'/180° F. 50 35.2  95/185      10 ZnB.sub.2 O.sub.3 10      46.5   46.5 7 VP      1:1.1 95 AH 480 20 .25 VD-1     ##STR4##      50 46.7  71/116 81   82   19.0  12.2 538      6 TiO.sub.2  1.0 P-40     oven        (281°

    Table II           Heat         Modified   Distor-      934  Smoke     Monsanto   tion   Visc-   Barcol Oxy- Den- Tunnel PSI×10.sup.3 PSI     Temp- Ex.  osity %  Hard- gen sity Test Flexural Flexural erature No.     Polyester PE/MON Resin/AH (cps.) Glass Catalyst Cure ness Index F-S     Front Back Strength Modulus (° F.)  11 10 EG/ 60/40 1:1   1250     20 .2 VD-1      ##STR5##      44 44.7  80/168   41.9   46.6 21.02  9.01 568  1 TMPDAE/ MMA    1.0 DDM     oven        (298° C.)  8 MA/2 AD 12 " 50/50 " 650 20 " " 50 44.1     59/107   41.9   51.4 22.7  11.40  552   MMA             (289° C.)     13 " 50/50 " 350 20 BPO oven 50 43.4  86/122 -- -- 21.08 10.32  --MMA 14     " 50/50 1:1.5 1530  20 BPO oven 37 57.5 102/152 -- -- 18.13  7.50  --     MMA 15 10 EG/ 50/50 1:1   360 20 .2 VD-1 RT 57 43.0  87/198   32.4     32.4 20.6  12.8 528  1 TMPDAE/ MMA    1.0 DDM         (276° C.)     10 MA 16 11.5 PG/ 50/50 1:1   290 20 BPO oven 55 36.1 112/175 48 60     23.94 15.23 500  10 F MMA             (260° C.) 17 " 50/50 1:1.5     1100  20 BPO oven 55 53.1 151/126 31 39 22.08 20.60 545   MMA      (285° C.) 18 " " " "" .2 VD-1 30'/180° F. 51 57.9 57/152     28 31 19.7  16.14 545       1.0 P-40 30'/250°      F.        (285° C.) 19 " 45/55 " 360 " BPO oven 52 48.8 106/146     24 44 18.21 16.46 525   MMA             (274° C.) 20 " 50/43 "     7000  " .5 VD-1 RT 52 52.4 116/121 43 43 13.32  9.40 525   MMA/    1.0     P-40         (274°

The percentages of polyester, methyl methacrylate and comonomer arepercentages by weight based on total weight of polyester, methylmethacrylate and comonomer.

With regard to the comonomers, the abbreviations in Table I stand for:

Sty = styrene

Ea = ethyl acrylate

Npgda = neopentyl glycol diacrylate

Vp = n-vinyl pyrrolidone

The resin/filler ratio is by weight.

The viscosity is measured in a Brookfield Viscometer at 25° C. using aNo. 2 spindle at 20 rpm.

The type of fiber glass used for reinforcement was 2 ounce choppedstrand mat and the percentage by weight is based on total weight ofresin (including filler) and fiber glass.

BPO represents benzoyl peroxide.

TBP represents tertiary butyl perbenzoate.

VD-1 represents cobalt octoate.

P-40 represents PERCADOX® 40 (Noury Chem.) described as a pentanedioneperoxide.

Unless otherwise indicated, 1 percent by weight catalyst is used.

DMA is dimethyl aniline.

An oven cure is generally at about 120° C. for about 15 minutes. RTmeans room temperature cure.

Barcol is a measure of hardness determined by a 934 Barcol Impressor. Itis a comparable measure of hardness using a scale of values of 0 to 100,and the higher the number, the harder the material.

OI is oxygen index, determined according to ASTM D-2863. D_(m)represents smoke density. F represents a flaming sample and S representsa smoldering sample. Smoke density is determined according to ASTMD-2843.

In the Modified Monsanto Tunnel Test, a sample 233/4 inches by 33/4inches is slanted at an angle of about 45° from the horizontal. Aspecified heat source is burned at the bottom of the sample and thesample then burned for four minutes. The flame spread, a function ofdistance and time, is then compared with a sample of redwood and a flamespread rating is reported. The test is similar to ASTM E-286, part 14(1974). Flame spreads for the front (F) and back (B) surfaces arereported.

The flexural strength and modulus is determined according to ASTM D-790.

The heat distortion temperature is determined according to ASTM D-648.

Some significant observations from the examples presented in Table Iabove are as follows.

By comparing Examples 1 and 2 at similar filler loading, the oxygenindex of the cured resin increases as the level of methyl methacrylateis increased and polyester decreased. Although the polyester in Example3 is kept at the same level as in Example 2, one-half of themethacrylate was substituted with styrene. This produced rathersubstantial changes since the oxygen index decreased unexpectedly whilethe smoke density increased very sharply. In a totally styrene thinnedexperiment (Example 4), the filled resin had a very high viscosity incomparison to Example 1 due to the poor solubility of this type ofpolyester in styrene compared to methyl methacrylate, while the curedresin again showed a very low oxygen index and a very high smokedensity.

The use of comonomers with methyl methacrylate can be carried outwithout greatly affecting the oxygen index of the system. Thus, ethylacrylate and vinyl pyrrolidone can be used to give faster reactivitywith the polyester and better overall cure without contributing greatlyto the oxygen index or smoke density (Examples 6 and 10). Where adifunctional monomer is used, such as in Example 7, the increase in thecrosslinking density renders more thermal stability to the system asexemplified by a higher heat distortion temperature and a lower flamespread than in Example 5. The oxygen index remained almost unchangedalthough the smoke density increased. Even at this level, this systemhas a lower smoke density than styrene based systems and a higher oxygenindex.

In Examples 8 and 9, other fire-retardant additives such as antimonyoxide and zinc borate can be incorporated and yet maintain a low smokedensity system. Their use, however, does not really reflect any dramaticimprovements in the oxygen index or the flame spread rating.

EXAMPLES 11 - 20

A second series of unsaturated polyesters cured for the most part withmethyl methacrylate were prepared. The principal variant in this seriesof polyesters was the formulation of the polyester itself. The polyesterformulation, the catalyst systems, time and temperature of cure, amountand type of filler, amount of fiber glass reinforcement, as well ascertain physical properties are reported in Table II above.

In the examples, the abbreviations for the polyesters are as follows:

Eg = ethylene glycol

Pg = propylene glycol

Tmpdae = trimethylol propane diallyl ether

F = fumaric acid

Ma = maleic anhydride

Ad = adipic acid

The polyesters were prepared in a manner generally described above inExamples 1-10, that is, all the ingredients were charged to a suitablereaction vessel equipped with a condenser, stirrer and a source ofnitrogen purging. The reactants were heated to initiate an exotherm andthe reaction continued with heating and nitrogen sparging to drive offwater.

At the completion of the polyesterification, the polyester is cooled toabout 155° C. under a nitrogen atmosphere at which time catalystpromoters and inhibitors, if used, are usually added. At about 90° C., acrosslinking agent is added to form the resin solution which is thencooled to room temperature and filtered to remove any gel particles.

The abbreviations used in Table II have the same significance asdescribed above in connection with Table I.

Some significant observations from the data presented in Table II aboveare as follows.

The resins of Examples 16-20 are formed from highly unsaturatedpolyesters giving the potential for more complete and room temperaturecures. However, with highly unsaturated polyesters such aspropylene-fumarate resins, the oxygen indices are relatively low. SeeExample 16 in which a propylene-fumarate resin at a 1:1 filler ratio hasan oxygen index of 36. This oxygen index should be compared with the oneobtained with an ethylene-propylene-maleate-adipate polyester such as isshown in Example 5 in which the oxygen index is 43.8. The oxygen indexof the propylene-fumarate resin can be improved if the hydrated aluminalevel is increased. See Examples 16 and 17; however, note also that theviscosity increases.

The effects of benzoyl peroxide on smoke density can be seen bycomparing Example 17 with Example 18. Example 17 contains benzoylperoxide and Example 18 employs a catalyst system of pentanedioneperoxide and cobalt octoate promoter. Benzoyl peroxide, being aromatic,appears to contribute significantly to the smoke density, whereas thealiphatic catalyst system of Example 18 appears to have minimal effecton the smoke density. Also, the benzoyl peroxide of Example 17 isapplied as a slurry in tricresyl phosphate which also is aromatic andcontains phosphate groups which are believed to contribute significantlyto smoke density.

EXAMPLES 21 - 27

The following examples show the dramatic effect of N-vinyl pyrrolidoneon accelerating curing so as to be able to achieve room temperaturecures.

EXAMPLE 21

An ethylene-propylene-maleate-adipate polyester was prepared asgenerally described in Examples 1-10. The polyester was blended withmethyl methacrylate to form a 1:1 weight ratio of polyester to methylmethacrylate. The resin was filled with aluminum hydrate in a 1:1 weightratio and cured at room temperature with a catalyst system consisting ofone percent by weight pentanedione peroxide and 0.2 percent by weightcobalt octoate promoter; the percentages by weight being based on resinweight. The resin gelled in 19.75 minutes and reached a peak exotherm of119° C. when 100 gram quantity was placed in a 150 milliliter glassbeaker and placed in a 66° C. bath with mild agitation.

EXAMPLE 22

Example 21 was repeated with the exception that 0.2 percent by weightdimethyl para-toluidiene was used in the catalyst system. The gel timewas reduced to 5.5 minutes but the peak exotherm was only 100° C.indicating an incomplete cure.

EXAMPLE 23

A resin system similar to Example 21 was prepared from the followingcharge:

    ______________________________________                                        Component             Percent by Weight                                       ______________________________________                                        Polyester + Methyl Methacrylate                                                                     47.5                                                     (50/50)                                                                      N-vinyl pyrrolidone   2.5                                                     TiO.sub.2             2.0                                                     Hydrated alumina      50.0                                                    ______________________________________                                    

As in Example 21, the catalyst system was one percent pentanedioneperoxide and 0.2 percent cobalt octoate. The gel test results are shownin Table III below.

EXAMPLES 24 - 27

Resin systems similar to Example 23 were prepared from the followingcharges:

    ______________________________________                                        Example No.   24      25       26     27                                      ______________________________________                                        polyester + methyl                                                                          47.5    46.5     46.5   46.5                                     methacrylate                                                                 N-vinyl pyrrolidone                                                                         2.5     3.5      3.5    3.5                                     TiO.sub.2     2.0     2.0      2.0    2.0                                     hydrated alumina                                                                            50      50       50     50                                      cobalt octoate.sup.1                                                                        0.1     0.1      0.05   0.2                                     pentanedione peroxide.sup.1                                                                 1.0     1.0      1.0    1.0                                     DMPT.sup.1                     0.01                                           ______________________________________                                         .sup.1 Percent by weight based on resin weight.                          

                  Table III                                                       ______________________________________                                        Example No.    23     24     25   26     27                                   ______________________________________                                        gel time, minutes                                                                            0.78   2.00   1.45  7.90  0.75                                  at 66° C.                                                             total time     1.30   3.42   2.42 11.60  1.25                                 peak temperature, ° F.                                                                 282    264    269  221    282                                 ______________________________________                                    

EXAMPLES 28 - 34

Hydrated alumina has a pronounced effect on oxygen index. Higherhydrated alumina loadings result in a higher oxygen indices. This isseen in FIG. 1 which is a plot of oxygen index versus percent hydratedalumina content of two different polyester resins.

Plot A represents an ethylene-propylene-maleate-adipate polyesterprepared as generally described in Examples 1-10 in a molar ratio of9/8/2.

Plot B represents a propylene-fumarate polyester prepared as generallydescribed in Examples 16 through 20 in a molar ratio of 11.5/10.

The polyesters were combined with 50 percent by weight of methylmethacrylate; the percentages by weight being based on total weight ofpolyester and methyl methacrylate, and filled with aluminum hydrate inthe various percentages shown in FIG. 1; the percentages by weight beingbased on total weight of polyester resin and hydrated alumina.

The filled resins were laminated with two layers of 2 ounce choppedstrand mat and cured at 82° C. for 30 minutes using 1 percent benzoylperoxide as the catalyst. After curing, the laminates were evaluated foroxygen index according to ASTM D-2863.

EXAMPLES 35 - 41

In order to develop adequate strength, the aliphatic polyesters of thepresent invention cured with aliphatic monomer, must be highlyunsaturated. Strength as a function of the percentage unsaturation isshown in FIGS. 2, 3 and 4. The resins evaluated for the data shown inFIGS. 2, 3 and 4 were prepared by blending 50 parts by weight polyesterwith 50 parts by weight methyl methacrylate, 7 parts by weight N-vinylpyrrolidone and 0.5 parts by weight cobalt octoate and 1.0 part byweight pentanedione peroxide.

The polyesters used in preparing the various resins were prepared fromthe following charges:

    ______________________________________                                        Component  Mole Ratios                                                        ______________________________________                                        maleic anhydride                                                                         10      9      8    7    6    5    4                               adipic acid        1      2    3    4    5    6                               ethylene glycol                                                                          9       9      9    9    9    9    9                               propylene  2       2      2    2    2    2    2                               ______________________________________                                    

The polyesters and resultant resins were prepared as generally describedin Examples 1-10.

The resultant resins were cast in a 12 inch by 12 inch by 1/8 inchclosed cell and allowed to gel at room temperature followed by aone-half hour post cure at 82° C. After curing, the resin castings werereleased from the cell and evaluated for flexural strength and modulusaccording to ASTM D-790 and for Barcol hardness using a 934 BarcolImpressor.

We claim:
 1. A curable aliphatic polyester resin, suitable for moldingand laminating, being essentially free of aromatic constituentscomprising a mixture of:A. an unsaturated aliphatic polyester derivedfrom polycondensing:1. organic polyols having a functionality of atleast 2,
 2. organic polycarboxylic acids having a functionality of atleast 2 in which the unsaturated component of the unsaturated polyesteris an alpha, beta-ethylenically unsaturated polycarboxylic acid and theequivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylicacid to all other polycarboxylic acid components in the polyester is atleast 1 to 1; and B. an aliphatic vinyl monomer which is a lower alkylester containing 1 to 4 carbon atoms of methacrylic or acrylic acid andwhich is copolymerizable with said polyester, C. at least 50 percent byweight hydrated alumina, the percentage by weight being based on totalweight of (A), (B) and (C),said composition capable of being completelycured to produce strong thermoset articles of construction which, whenburned, produce little smoke.
 2. The composition of claim 1 whichcontains:A. from 20 to 80 percent unsaturated aliphatic polyester, andB. from 80 to 20 percent aliphatic monomer,the percent by weight beingbased on total weight of unsaturated polyester and aliphatic monomer. 3.The composition of claim 1 in which the alpha, beta-ethylenicallyunsaturated polycarboxylic acid is maleic acid or its anhydride, orfumaric acid.
 4. The composition of claim 1 in which the organicpolycarboxylic acid component contains an acyclic saturatedpolycarboxylic acid or anhydride containing from 2 to 10 carbon atoms.5. The composition of claim 4 which contains:A. from 0 to 50 equivalentpercent of an acyclic saturated polycarboxylic acid or anhydridecontaining from 2 to 10 carbon atoms, and B. from 50 to 100 equivalentpercent of an alpha, beta-ethylenically unsaturated polycarboxylic acidor its anhydride.
 6. The composition of claim 1 in which the polyolcomponent includes alcohols or polyols containing allylic or acrylicunsaturation.
 7. The composition of claim 6 which includes trimethylolpropane diallyl ether.
 8. The composition of claim 1 in which the polyolcomponent is an alkylene glycol or an alkylene oxide glycol containingfrom 2 to 10 carbon atoms.
 9. The composition of claim 1 in which thepolyol component contains in part a polyol having a functionalitygreater than
 2. 10. The composition of claim 1 in which the aliphaticmonomer contains a fully esterified polyol.
 11. The composition of claim1 in which the aliphatic monomer includes in part N-vinyl pyrrolidone.12. The composition of claim 1 which further includes antimony oxide.13. The composition of claim 1 which contains:A. 75 to 25 percent byweight aliphatic polyester resin; and B. 25 to 75 percent by weighthydrated alumina,the percentages by weight being based on total weightof aliphatic polyester resin and hydrated alumina.
 14. The compositionof claim 13 which further includes about 10 to 70 percent by weightglass fibers; the percentage by weight being based on total weight ofaliphatic polyester resin, hydrated alumina and fiber glass.
 15. Thecomposition of claim 1 in a cured, crosslinked state.
 16. Thecomposition of claim 14 in a cured, crosslinked state.